Metabolic disorders, such as obesity and type 2 diabetes, are quickly becoming a major public health problem not just in the United States but all over the world. Lipotoxicity, the cellular dysfunction caused by excess lipid accumulation in body tissues, has been implicated to play a role in such disorders. Investigation of the molecular mechanisms involved in lipotoxic cell death will bring a more detailed understanding of these diseases and allow for novel therapeutic possibilities. Lipotoxicity refers to the deleterious accumulation of excess fatty acids (FA) in non-adipose cells resulting in cellular dysfunction and cell death. In order to identify genes involved in lipotoxicity we conducted a selection for mutant cell lines resistant to fatty acid (FA)-induced cell death. We identified ribosomal protein L13a as a potential mediator of lipotoxicity. L13a has been reported to play a role in translational regulation. In the following three aims, I will test the hypothesis that ribosomal protein L13a plays a role in the FA-induced stress response mechanism by regulating the translation of distinct transcripts that lead to the induction of apoptosis. In addition, I hypothesize that during lipotoxic conditions in vivo, L13a deficiency will protect against cell death in a model of lipotoxic heart disease and protect against the development of metabolic cardiomyopathy. In Aim I, I will use the LISa-deficient Chinese Hamster Ovary (CHO) cell line to demonstrate a specific role for L13a in FA- induced cell death. I confirm this phenotype independently by siRNA-mediated directed knockdown. In Aim II, I will investigate the function of L13a during lipotoxic conditions, assessing a possible role for L13a in translational regulation during lipotoxic conditions. I will compare changes in reporter transcript expression and subcellular localization of L13a in WT and LISa-deficient mutant cells under lipotoxic conditions. In addition, I will use a proteomic approach to identify genes that are differentially regulated during lipotoxic conditions. In Aim III, I will examine the effects of L13a deficiency in the context of a mouse model of high- fat diet induced liver lipotoxicity. I will also breed the L13a haplo-insufficient mouse to a mouse with heart- specific overexpression of ACS (acyl-CoA synthetase) that develops cardiac failure due to cardiomyocyte lipid overload. I will then directly assess cardiomyocyte survival and overall heart function in adult animals. [unreadable] [unreadable] [unreadable]